Mr. Slim, the Mexican telecom billionaire and The New York Times‘ largest creditor, is in contract to buy the building, at 417 Fifth Avenue, for $140 million, or $343 a square foot, from Joseph Moinian and Goldman Sachs, which purchased the building for $250 million during the height of the real estate boom.

The sellers’ brokers at Cushman & Wakefield declined to comment, as did a representative for Mr. Moinian.